1. Field of the Invention
The invention relates to a coating method, whereby a metal coating is deposited from a vapor flow at reduced pressure onto a flat metal substrate retained by a substrate holder, and the vapor particles are evaporated by means of at least one energy source comprising at least one container constituting an evaporation source, a strip-shaped, flat preliminary product for producing a bearing element with a metal substrate on which at least one metal layer is disposed, as well as devices for coating a flat, metal substrate in the gas phase with a metal layer formed by a vapor flow at reduced pressure, comprising a vacuum-sealed housing, a drum-shaped substrate holder, at least one electron beam evaporator for generating the vapor flow and at least one container constituting an evaporation source for the particles.
2. Prior Art
Methods of depositing metal coatings o a metal substrate under vacuum have long been known. For example, patent specification DE 195 14 835 C1 discloses a method of applying a coating to concavely curved sliding elements by vacuum deposition. To this end, a specific distance is set between the substrate and the surface of the evaporator bath. The material to be deposited is disposed in evaporator pans and is evaporated by an electron beam. As the coating is being deposited, the evaporator and the support body are moved relative to one another at a non-uniform speed. The speed of the linear movement reaches its maximum component both on entering and leaving this vapor beam. In order also to ensure that the coating thickness of the deposited coating does not deviate from the maximum coating thickness by more than 15%, parts of the vapor flow are screened with the aid of screens.
The disadvantage of this type of vapor deposition is that the coating thickness is set on the basis of several parameters which have to be adapted to one another and a relatively complex motion sequence has to be predefined, monitored and controlled. Structural measures also have to be taken in order to achieve the desired ratio of coating thickness. Moreover, if an alloy is used for the coating to be created, it must already be present in the evaporator source. Another disadvantage, amongst other things, is the fact that material can accumulate at certain points.
Patent specification DE 197 53 656 A discloses a system for vacuum coating plain bearings with at least one intermediate coating and at least one anti-friction coating, comprising a series of vacuum chambers disposed in a row one after the other and separated by vacuum valves or pressure stages, at least one vacuum chamber serving as a gating chamber for introducing the uncoated plain bearings and/or discharging the coated plain bearings into and out of the vacuum, and at least one other vacuum chamber being used to pre-treat the uncoated plain bearings by means of a plasma process, and at least one respective vacuum chamber being used to apply the intermediate coating and the anti-friction coating, as well as vacuum pumps connected to the vacuum chambers, power supply and control systems for running the coating processes and means for conveying several plain bearings on a conveyor track running through the system, and the plain bearings are positively retained in a support body, which support bodies can be heated, and the plain bearing can be pressed into the support bodies with an adjustable force, and, disposed one after the other in the conveying direction, are at least the gating chamber, a pre-treatment chamber, a first coating chamber, a second coating chamber and a gating chamber, and the control system is configured so that the support bodies can be moved at a speed which can be adapted to a part-process taking place in each vacuum chamber, and the pre-treatment chamber has an etching device for etching the friction bearings by a stationary plasma process assisted by a magnetic field, the first coating chamber has a magnetron-atomizer source in which at least one target disposed underneath and at a distance from the plain bearings is disposed and is adapted to the geometry of the plain bearings, the second coating chamber contains an electron beam evaporator with an evaporator pan, disposed at a distance from the plain bearings adapted to their geometry, and buffer regions are provided before and after the region in which the plain bearings are exposed to the electron beam vapor deposition process.
The specific disadvantage of this system is the complex structure and the need to provide specially shaped support bodies for the plain bearing shells, in view of the fact that these supports have to be specially made available for every plain bearing diameter in order to guarantee the appropriate contact pressure
Other electron beam vapor deposition methods used for plain bearing shells are known from patent specifications DE 198 24 308 A and DE 198 24 310 A, for example.